It is known, for the preparation of hot drinks such as coffee or tea, to use machines comprising an infusion circuit in which the water is heated to a temperature of about 90 degrees Centigrade or more, and is injected into an infusion chamber containing the infusion product. The infusion product may be, for example, in the form of powder or leaves, or contained inside capsules or tablets.
Machines of the type described above, in particular for professional use in bars, have the disadvantage of using boilers for heating a liquid, in particular water, for the preparation of a plurality of different beverages that require different quantities of hot liquid. For example, boilers of professional machines of known type heat water for the preparation of tea or coffee; it is therefore known to use boilers with a tank configured to heat several litres of water, in order to ensure operation even at full machine load for long periods of time so as to avoid creating long waiting times. This inevitably causes a great waste of energy, since it is necessary to keep the boiler in constant operation to prevent the liquid contained in it cooling down. In some cases, machines of the professional type described above are kept switched on even during the night when they are not in use, to avoid cooling and long start-up times in the morning.
Furthermore, machines of the known type have the disadvantage that the boilers maintain their own internal hot water at a temperature close to boiling point to also allow the production of steam for creating foaming liquids such as cream or milk. Therefore, the water contained for prolonged times in these boilers has the disadvantage that the salts in the water contained in the tank precipitate towards the bottom of the boiler and therefore there is water rich in mineral salts at the bottom of the boiler and water free of mineral salts in the upper part. This diminishes the organoleptic properties of the water and consequently also the taste and the final quality of the infusion.